1. Field of the Invention
The present invention refers to a shaft seal ring formed of a polytetrafluoroethylene (PTFE) compound or of a material which is similar with regard to the sealing behaviour or durability, comprising a sealing lip and a protective lip integrally formed therewith, as well as to a method and a device of manufacturing a shaft seal ring of that kind.
2. Description of Prior Developments
It is known (from DE-OS 24 60 185) to provide a shaft seal without a protective lip. On the side of the sealing lip facing the shaft embossed recesses having the shape of screw lines or threads are formed for returning oil to the oil side of the seal.
The recesses are embossed by a separate embossing tool into a seal wafer cut from a PTFE compound tube. The wafer is subsequently brought into final shape with a final embossing tool.
A shaft seal ring of the above-mentioned kind is also known from DE 33 27 229 A1 in which a protective lip integrally formed with the sealing lip is first peeled out of the PTFE compound on the front side of a plate. After forming a recess into the front side of the sealing lip adjacent the protective lip, cuts are made in the radial and in the axial direction. These cuts increase the flexibility of the seal and generate a return flow effect of the oil away from the sealing edge.
Finally, a shaft seal ring made of a PTFE compound is known from DE 36 07 662 A1 wherein the flexibility of the sealing lip is increased by cuts made on the two sides of the sealing lip the cuts are offset with respect to one another by half of the cut distance.